CNS/PNS Intro, CNS Embrology Flashcards
1
Q
3 Planes to section the brain and spinal cord
A
1) coronal plane
2) sagittal plane
3) axial plane
2
Q
Locations of Neuro Lesions
A
-Left/Right
-Rostral/Caudal
Forebrain, Hindbrain, Brainstem, Spinal Cord, Nerve Root, Peripheral Nerve, Nerve Muscle Junction, Muscle
3
Q
Telencephalon
A
-includes cerebral hemishperes
4
Q
Diencephalon
A
-hypothalamus & thalamus
5
Q
Mesencephalon
A
-midbrain
6
Q
Metencephalon
A
-pons & cerebellum
7
Q
Rhombencephalon
A
-medulla
8
Q
“Gray Matter”
A
- CNS regions with high packing densities of neurons
- appear darker
- much is on the surface of the brain
- located deep/center of the spinal cord
9
Q
“White Matter”
A
- regions with higher densities of axons (high fat content and myelin covering that acts as insulation)
- appear lighter
- all lies deep in the brain
- located on surface of spinal cord
10
Q
5 Major Subdivisions of the Forebrain
A
1) frontal
2) parietal
3) temporal
4) limbic
5) occipital
11
Q
Basal Ganglia
A
-involved in smoothing out motor movements of the limbs & axial musculature during body movement
12
Q
Thalamus
A
- involved as a relay center for all external sensory information being passed along to the forebrain
- important regulatory center along with the hypothalamus for the autonomic nervous system
13
Q
Main Components of the Brainstem
A
- midbrain
- pons
- medulla (connects brain to spinal cord)
14
Q
How many cervical spinal cord segments are there?
A
8, only 7 vertebrae
15
Q
How many thoracic spinal cord segments?
A
12, 12 vertebrae
16
Q
How many lumbar spinal cord segments?
A
5, 5 vertebrae
17
Q
How many sacral spinal cord segments?
A
5 - fused with sacral vertebra making sacral bone
18
Q
What happens with spinal cord as child grows?
A
-its pulled rostrally so the lower thoracic, lumbar, and sacral nerves exit the spinal canal several segments below their exit from the spinal cord
19
Q
Where does the spinal cord end?
A
-T12-L1 vertebrae
20
Q
Grey matter organization in spinal cord?
A
–bilateral dorsal horns and bilateral ventral horns
21
Q
Dorsal Root of Spinal Cord
A
-serves afferent (peripheral sensory nerve fibers traveling to the cord)
22
Q
Ventral Root of Spinal Cord
A
-serving efferent (motor nerves traveling to muscles, organs, etc.)
23
Q
Only Motor CNS pathway to the Periphery?
A
- corticospinal or pyramidal pathway
- originates in large Betz cells in motor cortex of forebrain which send fibers or axons through the posterior limb of the internal capsule down the brainstem where they decussate (switch to opposite side) before descending through the lateral spinal cord as the lateral corticospinal tract
- axons terminate in a connection called synapse
- neuron located in anterior horn (lower motor neuron)
24
Q
Spinothalamic Tract
A
- serves sensations of pain & temperature from the periphery
- cell body of pathway (pseudounipolar) lies in the dorsal root ganglion
- neuron sends one axon to periphery where its special nerve endings sense pain & temp and a central extension of the same axon into the spinal cord (axon synapses to 2nd neuron in gray matter of dorsal horn)
- 2nd neuron sends axon to opposite side & travel rostrally through the spinal cord to synapse with 3rd neuron lying in ventral posterior nucleus of the thalamus
- 3rd neuron sends its axon to neurons lying in the sensory cortex of the forebrain to complete pathway
25
Dorsal/Posterior Column Pathway
- informs brain of the position of body parts in space
- origin from psuedounipolar neurons lying in dorsal root ganglia
- one portion of the axon ends in periphery as a special sensory terminal that detects vibration & position changes and the other end of the axon enters the spinal cord and travels rostrally on the same side of the cord up to the medulla of the brainstem where it synapses to a 2nd neuron in either the gracile or cuneate nuclei
- 2nd neuron sends its axon across to the opposite side & up to the ventral posterior lateral nucleus of the thalamus where it synapses on a 3rd neuron
- the VPL neuron sends its axon up to the sensory cortex to synapse on a cortical neuron
26
Beginning of Brain Development
-in 3rd week of gestation with the formation of the neural tube & crest cells
27
3 Layers of the Embryo
1) Endoderm: internal organs
2) Mesoderm: muscle & skeleton
3) Ectoderm: skin & nervous system
28
When in development are the Telencephalon, Diencephalon, Mesencephalon, Metencephalon, & Myelencephalon identifiable?
- by 5 weeks gestation
| - these are structures that have corollaries in the adult brain
29
CNS Structures formed by Week 3?
-neural plate
30
CNS Structures formed by Week 4?
- neural tube
- closure of the anterior (25 days) and posterior (27 days) pores
- 3 primary brain vesicles formed (Prosencephalon, Mesencephalon, Rhombencephalon)
31
CNS Structures formed by Week 5?
-5 primary brain vessels formed (Telencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon)
32
CNS Structures formed by Week 8?
-cerebral hemispheres enlarged
33
Neurogenesis & Migration
- neuroblasts & glioblast are generated in the ventricular zone & migrate out to their final location where they aggregate to form adult structures
- Radial glial cells serve as guide wires for the migration of neurons
- migrating neurons attach to & travel along the radial glial cells to their final destination
34
Ventricular zone neuroepithelial cells differentiate into?
- neuroblasts
| - glioblast
35
What do neuroblasts form?
-all neurons found in the CNS
36
What do glioblasts form?
-radial glial cells, astrocytes, oligodendrocytes, ependymocytes, tanycytes, & choroid plexus cells
37
When are glial cells formed?
- Radial glial cells: before neuroblasts differentiate into neurons
- others: after neuroblast formation is complete
38
Microglia arise from?
-monocytes in the circulation & invade the CNS during the 3rd week with the formation of cerebral blood vessels
39
What separates the alar plate from the basal plate?
-the sulcus limitans
40
Sulcus Limitans in adult brain stem?
-separates sensory brain stem nuclei from motor brain stem nuclei
41
What does neurogenesis in the alar plate do?
- forms the sensory neurons & nuclei of the spinal cord and the brain stem
- Dorsal root ganglia neurons
42
What does neurogenesis in the basal plate do?
-forms the motor neurons & nuclei of the spinal cord & brain stem
43
Differential Growth Rate of Spinal Column vs. Spinal Cord?
- Column (elongates faster)
- Cord (elongates slower)
- results in apparent rostral migration of conus medullaris during fetal development and after birth until the adult position of the conus medullaris is reached
44
Conus Medullaris
-end of spinal cord
45
Location of Conus Medullaris in 3 month fetus?
-end of spinal column
46
Location of Conus Medullaris in 6 month fetus?
-spinal column begins to outgrow the cord & it ends at vertebral sacral 1
47
Location of Conus Medullaris in 9 month fetus?
-ends at vertebrae lumbar 3
48
Location of Conus Medullaris in adult?
-ends at lumbar 1-2
49
Anencephaly
| Encephalocele
-failure of the anterior neural pore to close
50
Spina Bifida
Meningocele
Myelomeningocele
-failure of the posterior neural pore to close
51
Neural Tube Defects are Associated with?
- folic acid deficiency in the mother
- take supplements early in pregnancy (first few weeks), reduce incidence
- failure of closure allows alpha-fetal protein to leak out into the amniotic fluid & into the blood stream of the mother (useful test)
52
Spinal Dysraphism
(spina bifida)
- Occulta: involves failure of mesodermal cells to form the bony dorsal vertebrae that surrounds the spinal cord (rarely develop neurologic symptoms), meninges & spinal cord/filum terminale are not involved, tuft of hair over lumbar-sacral area or a sinus tract
- Aperta: meninges extend into the outpouching and into myelomeningocele the spinal cord/terminale & the meninges extend into the outpouchin
- more commonly causes neurologic symptoms which may be severe
53
Arnold Chiari Malformation
-displacement of the cerebellar tonsils below the foramen magnum
Type 1: herniated cerebellar tonsils
Type 2: herniated cerebellar tonsils + cervical or occipital encephalocele
